Re: sync()

Kurt Roeckx wrote:
> [SIO] [Option Start] If _POSIX_SYNCHRONIZED_IO is defined, the
> fsync() function shall force all currently queued I/O operations
> associated with the file indicated by file descriptor fildes to the
> synchronized I/O completion state. All I/O operations shall be
> completed as defined for synchronized I/O file integrity
> completion. [Option End]

Hmmm....so if I consistently want these semantics out of fsync() I
have to #define _POSIX_SYNCHRONIZED_IO? Or does the above mean that
you'll get those semantics if and only if the OS defines the above for
you?

I certainly hope the former is the case, because the newer semantics
which you mentioned in the section I cut don't do us any good at all
and we can't rely on the OS to define something like
_POSIX_SYNCHRONIZED_IO for us...

Being able to open a file, do an fsync(), and have the kernel actually
write all the buffers associated with that file to disk could be, I
think, a significant performance win compared with the "flush
everything known to the kernel" approach we take now, at least on
systems that do something other than PostgreSQL...

--
Kevin Brown kevin(at)sysexperts(dot)com